Turn on the heater full blast.. This pulls heat off the engine. Then keep an eye on the gauge to see if it changes. Of course, if the car overheats while the air conditioner is on, turn the A/C off immediately since it taxes the engine. Coasting can also help cool the engine if you can't pull over right away. REMEMBER not to ever remove the radiator cap on a hot engine or you'll risk explosive heat. The cap maintains pressure so removing it when the car is hot is like opening a volcano.

If you'll be sitting idle for more than 90 seconds, like at a train crossing or drive-thru, pop your automatic transmission into neutral. This takes some of the strain off the engine and lets it rest a bit.